1. Field of the Invention
The present invention relates to a slim type stator and motor, and more particularly, to a slim type stator, a method of making the same, a slim type motor having the same, and a direct drive apparatus for use in a drum-washing machine.
2. Description of the Related Art
In general, a drum-washing system performs washing using a frictional force between a rotating drum and washes according to a delivered motor drive force, at a state where a detergent, cleaning water, and washes are engaged in a drum, to thereby cause few damages of washes, and prevent washes from getting tangled, and provide an effect of washing washes by striking and rubbing the washes.
Conventional drum-washing machines are classified into an indirect drive system in which a drive force of a motor is transferred to a drum indirectly through a belt that is wound between a motor pulley and a drum pulley, and a direct drive (DD) system in which a shaft that is connected to a rotor of a brushless direct-current (BLDC) motor is connected directly to a drum, so that the motor drive force is immediately transferred to the drum.
Here, a belt-pulley drive system that does not transfer a drive force of a motor directly to a drum but transfers the motor drive force through a belt that is wound between a motor pulley and a drum pulley causes an energy loss during a transfer process of a drive force and generates much noise during a transfer process of power.
Therefore, to solve problems of such an existing drum-washing machine, use of a direct drive type drum-washing machine that uses a BLDC motor is being expanded.
Meanwhile, a core type BLDC motor has a structure that a magnetic circuit is symmetrical to a radial direction around an axis, and thus generates less axial vibratory noise. Accordingly, the core type BLDC motor is suitable for low speed rotation. In addition, a portion where a gap occupies for direction of a magnetic path is few in the case of the core type BLDC motor. Accordingly, the core type BLDC motor can get a high flux density even if magnets of a low magnetic performance are used or a quantity of magnets are reduced. As a result, the core type BLDC motor has advantages of a big torque and a high efficiency.
However, such a core structure, that is, a yoke structure may cause a material loss of a yoke when manufacturing a stator. In addition, a special expensive dedicated winding machine should be used in order to wind coil on the yoke due to a complex structure of the yoke when mass-producing. In addition, a mold investment cost is high at stator manufacturing to thus cause a high facility investment cost, in the case of the core type BLDC motor.
In the core type alternating-current (AC) or BLDC motor, especially the radial type core motor, it is a very important factor that decides competitive power of a motor to form the stator core into a perfect division type, since coil can be wound on division cores at a high efficiency using an inexpensive general-purpose winding machine. However, on the contrary, a low efficiency winding operation is performed using an expensive dedicated winding machine, in the case of an integrally built-in type stator core. Accordingly, a manufacturing cost of a motor is heightened in the case of the integrally built-in type stator core.
It may cause a problem that does not form a perfect magnetic circuit when the stator core is combined with a single rotor, to form the stator core into a perfect division type in order to get an effectiveness of coil winding, in the case of the radial type core motor.
Considering this point, a structure of greatly heightening productivity of stator assembly was proposed by the same applicant as this invention in the Korean Laid-open Patent Publication No. 2005-0000245, that includes: an annular core support plate that makes a number of division core assemblies on which coils are wound accommodated at a certain interval and supported in respective bobbins, and simultaneously a number of coils connected per phase; and an automatic position set/support unit that makes the division core assemblies automatically position set and supported at a certain interval.
In the case of the above-described motor, the core support plate 14 is arranged on the lower portion of the stator, to thus provide a connection space to connect between coils that are wound on a number of division stator cores. In addition, since an electric power terminal block for supplying electric power for motor coils is projected from a stator holder, the motor was produced thickly in which the whole thickness of the motor is about h=63 mm. Also, since a drum diameter of the drum-washing machine is as large as 220-260 mm in the case that the above-described motor is applied to a drum-washing machine, diameter of the annular core support plate should be also large in proportion to the drum diameter. As a result, the above-described motor is very disadvantageous in view of a manufacturing cost and an assembly of the annular core support plate.
Since the whole thickness of the motor is thick as described above, it is required in order to make the motor into a thin film structure that a number of stator cores on which coils are wound should be integrated by insert-molding using a thermosetting resin preferably without using the above-described annular core support plate.
Meanwhile, in the case of a large-size motor, a number of stator poles and a number of rotor poles are usually mixed. When the motor employs a division core system, a successive winding on cores of a number of group made of a number of division cores to then assemble the number of the division cores is desirable than an individual winding on a number of division cores to then assemble the number of the division cores, in view of assembly productivity.
The technology of manufacturing a motor by assembling a number of division cores without using any annular core support plate by this successive winding was disclosed in the Korean Patent Registration No. 663641 to the same applicant as that of this application.
Further, three-phase coils (U, V, and W) are connected with an electric power terminal block through three lead wires, in the case of the conventional motor for use in a washing machine. One end of the lead wires is connected to the terminal block by soldering, and the other ends of the lead wires are connected to one end of the respective three-phase coils (U, V, and W).
However, the lead wire connection structure between the electric power terminal block and the three-phase coils may cause the following defects. When the lead wires are insert-molded together with a number of cores at a state where the lead wires are soldered together with three-phase coils, the lead wires are flexible and thus do not maintain a constant shape. As a result, since it is difficult to fix the lead wires, an insert-molding work for integrating temporarily assembled division core assemblies is not smoothly performed, to thereby cause workability to be lowered. Due to these reasons, overall man-power required increases and a work efficiency is lowered. As well, a motor manufacturing cost is elevated and defective products may be caused.